The present invention relates to an ophthalmic characteristic measuring apparatus.
As a conventional cornea shape measurement apparatus, an apparatus is known in which an index is projected on a subject eye, an imaging position of the index is obtained, and a cornea shape is measured. Besides, as an apparatus for measuring optical characteristics of an eye, in Japanese patent application assigned to the present assignee, an apparatus is disclosed in which a focus adjustment of an illumination optical system is carried out with a received light level measured through a Hartmann plate, and a focus adjustment of a light receiving optical system is carried out on the basis of optical characteristics (S) obtained from its received light output (see Japanese Patent Application No. 137630/1997).
However, in the conventional apparatus for measuring the optical characteristics of the subject eye, only correction of glasses can be carried out, and there has been a case where it can not be said that desired oohthalmic characteristics can be sufficiently measured. Besides, in the conventional ophthalmic characteristic measuring apparatus, there is a case where from a difference in the reflectivity of an eyeground intrinsic to each eye and in the transmittance of an eyeball optical system, each spot of a Hartmann image is saturated or the amount of light is insufficient, and it is difficult to precisely set an exposure amount, an exposure time or a light amount of a light source, and it is expected that it is difficult to measure accurate oohthalmic characteristics. Incidentally, in general, exposure amount=(exposure timexc3x97light amount of light source).
In view of the above, an object of the present invention is to provide an ophthalmic characteristic measuring apparatus which can adjust an exposure amount, such as an exposure time or a light amount of a light source, at the time of wavefront measurement.
According to the present invention, an ophthalmic characteristic measuring apparatus comprises
a first light source section for emitting light flux with a first wavelength,
a first illumination optical system for illuminating a minute area on a retina of a subject eye with the light flux from the first light source section,
a first light receiving optical system for guiding a part of first reflected light flux reflected and returned from the retina of the subject eye to receive it through a first conversion member for converting the first reflected light flux into substantially at least 17 beams,
a first light receiving section for receiving the received light flux of the first light receiving optical system to form a first signal,
a second light source section for emitting light flux with a second wavelength,
a second illumination optical system for illuminating an eyeground of the subject eye with the light flux from the second light source section and with a predetermined pattern,
a second light receiving optical system for guiding second reflected light flux reflected and returned from the eyeground of the subject eye to receive it,
a second light receiving section for receiving the received light flux of the second light receiving optical system to form a second signal,
an arithmetic section for obtaining a wavefront of the light flux reflected from the subject eye on the basis of the first signal from the first light receiving section, and obtaining refractive power of the subject eye on the basis of the second signal from the second light receiving section, and
an exposure amount determination section for determining an exposure amount of the first light receiving section on the basis of the second signal of the second light receiving section.